1. Field of the Invention
The present invention relates to a circuit arrangement for generating square-shaped signals from sinusoidal signals with the aid of a hysteresis inflicted comparator circuit.
2. Description of Related Art
It is known to generate a square-shaped signal from a sinusoidal signal which square-shaped signal exhibits steep edges precisely at the zero crossings of the sinusoidal signal. Such a signal is suitable, for example, for switching electronic stages because it constitutes an unambiguous switching function. However, an ideal square-shaped signal ensues only in case of undisturbed input signals, i.e. which are not superimposed by disturbing oscillations. As known in the art, these cause several edges in the vicinity of the zero crossings which can be compared with contact chatter of mechanical switch contacts. Therefore, an unambiguous switching function is no longer ensured. In order to eliminate this disadvantage it is known to provide the comparator at which the square-shaped signals ensue with a switching hysteresis as described, for example, in the book by Tietze/Schenk, 4th edition, page 133/134. The effect of this switching hysteresis is that an unambiguous switching edge is not generated until an upper minimum value of the input voltage is exceeded or, respectively, when a drop below a lower minimum value of the input voltage occurs. Hereby, however, the possibility is accepted that the switching edges of the square-shaped output signal no longer temporally coincide with the zero crossings of the input signal.